Physics 1

• Scalar quantity

  A quantity with magnitude (but no direction), such as distance, speed, mass, temperature
• Vector quantity

  A quantity with magnitude and direction, such as forces, velocity, acceleration, momentum
• Vector arrows

  Vectors can be represented by arrows pointing in the right direction: longer arrow = bigger force
• Velocity

  Your speed in a certain direction. Units are m/s (metres per second)
• Calculate velocity (speed)

  1. Velocity = distance / time

  2. v = x/t

  3. Speed = m/s

  4. Distance = m

  5. Time = s
• Distance-time graphs


  • Graph with time on the x-axis, distance travelled on the y-axis:
  • Sloping up = moving away
  • Horizontal = stationary
  • Sloping down = moving back
  • Speed = change in y / change in x
• Acceleration


  Changing velocity. Units = m/s2 (metres per second squared). Velocity changes when you change speed or direction
• Velocity-time graph


  • Time: x-axis, Velocity or speed: y-axis
  • Sloping up = accelerating
  • Flat = constant velocity or speed
  • Sloping down = decelerating
  • Gradient = acceleration
  • Area = distance travelled
• Resultant force


  The total force that results from two or more forces acting upon a single object.
• Newton's first law of motion

  • An object will move at the same speed and direction unless it experiences a resultant force.
  • Resultant force: object changes velocity (speed or direction)
  • No resultant force: object stay at same velocity
• Force


  A push or a pull, unit are newtons, 'N'. Measured with a force meter
• Mass vs weight


  • Mass: the amount of matter an object is made of, units are 'kg'.
  • Weight: the force created by gravity pulling down on a mass, units are 'N'
• Gravitational field strength


  The strength of gravity, which is different on different planets. Units = newtons per kilogram, N/kg
• Calculate weight


  1. Weight = mass x gravitational field strength

  2. W = m x g

  3. Weight = N

  4. Mass = kg

  5. Gravitational field strength = N/kg
• Newton's second law of motion

  • Force = mass x acceleration
  • F = m x a
  • Force = N
  • Mass = kg
  • Acceleration = m/s2
• Newton's third law of motion

  • For every action force there is an equal but opposite reaction force.
  • Action force: the force you push with
  • Reaction force: a force of the same size in the opposite direction to the action force
• Momentum


  The tendency of an object to keep moving
• Calculate momentum


  1. Momentum = mass x velocity

  2. p = m x v

  3. Momentum = kg m/s

  4. Mass = kg

  5. velocity = N/kg
• Momentum and force calculations

  1. Force = change in momentum / time

  2. F = (mv - mu)/t

  3. Force = N

  4. Mass = kg

  5. Velocity = m/s

  6. Note: mv = final momentum, mu = initial momentum

  7. Time = s
• Describe energy transfers

  Say what form the energy starts as and what it becomes
• Energy


  The capacity to do work. Units are joules, 'J'. 1 kJ = 1000 J
• Energy efficiency


  • The proportion of energy that a device transfers to a useful form.
  • Efficiency = useful energy out / total energy in
• Convection


  Heat transfer caused when hot fluids (gas or liquid) rise because they are less dense
• Conduction

  Heat transfer through solids caused by vibrating particles bumping into each other
• Radiation

  Heat transfer by infrared radiation which heats objects up when they absorb it
• Calculate kinetic energy

  1. KE = ½ mv2

  2. Where:'KE' is kinetic energy in J

  3. 'm' is mass in kg

  4. 'v' is velocity in m/s
• Calculate gravitational potential energy

  1. GPE = m x g x h

  2. Where 'GPE' is gravitational potential energy in J, 'm' is mass in kg, 'g' is gravitational field strength in N/kg, 'h' is height change in m
• Renewable energy resources

  • wind
  • solar
  • hydroelectric
  • tidal
• Non-renewable energy resources

  • fossil fuels (coal, oil, natural gas)
  • nuclear
• Waves

  Transfer energy without transferring matter by particles oscillating (vibrating back and forth)
• Transverse waves


  Waves in which particles oscillate at right angles to the direction of energy movement. E.g. water waves and light waves
• Longitudinal waves


  Waves in which particles oscillate parallel to the direction of energy movement. E.g. sound waves
• Quantities for describing waves

  • Wavelength - length in m from the top of one wave to the top of the next
  • Frequency - number of waves per second in hertz, HZ
  • Period - the time a single wave takes to pass
  • Amplitude - the height from the middle to the top of a wave
• Calculate wave speed from frequency and wavelength

  1. Wave speed = frequency x wavelength

  2. v = f x λ

  3. Speed = m/s

  4. Frequency = Hz

  5. Wavelength = m
• Refraction

  Bending of waves when they enter a new medium at an angle, caused by changing speed
• Electromagnetic waves

  Transverse waves that travel at the speed of light (300,000,000 m/s)
• EM spectrum in order (lowest to highest frequency / energy)

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Uses of EM radiation: Radio waves

  • TV, radio, satellite communications
• Uses of EM radiation: Microwaves


  • mobile phone, satellite communications
• Uses of EM radiation: Infrared

  • toasters/grills, remote controls, night vision